1. Field of the Invention
The present invention relates to a sensing unit and a method of making the sensing unit.
2. Description of the Related Art
A silicon acceleration sensor employing MEMS technology is known from the prior art as an acceleration sensor (accelerometer).
A sensing unit of this silicon acceleration sensor is typically made through a process such as that shown in FIG. 11. More specifically, when making a sensing unit 110 of the silicon acceleration sensor, first, as shown in (a) of FIG. 11, a photomask 102 having a pattern of stripes arranged in parallel is formed on a silicon substrate 100. Deep etching (at an etching depth of 25 to 30 μm) using the photomask 102 is then performed, thereby forming a plurality of parallel trenches 104. Then, as shown in (b) of FIG. 11, an SiO2 film 106 is deposited on an upper surface of the substrate 100 and an inner wall surface of the trenches 104. Next, as shown in (c) of FIG. 11, a bottom surface part of the trenches 104 is partially removed by isotropic etching such that adjacent trenches 104 are connected to each other by the bottom surface part. As a result, a cantilever part 108 capable of reciprocating in a single parallel direction (in other words, the arrangement direction) to the surface direction of the substrate 100 is formed between the adjacent trenches 104.
In the sensing unit 110 having the structure shown in FIG. 11, acceleration is measured on the basis of variation in electrostatic capacity accompanying oscillation of the cantilever part (movable part) 108.